Screen printing press

ABSTRACT

An improved screen printing press having a first frame with a surface to receive work for printing and a second frame pivotally mounted on the first frame and having a pair of spaced-apart support arms for movement therewith toward and away from the surface, a chase pivotally mounted on the first frame beneath the arms, and movable therewith, a screen removably mounted on the chase, a carriage assembly means, with a squeegee and a flood bar, mounted for reciprocal movement on the arms, the second frame also having, at a rear portion thereof, a press drive means operatively connected to drive arms mounted for pivotal movement on the first frame to drive the carriage assembly means. The second frame pivots with respect to the first frame about an axis in the plane of the work surface to eliminate smearing during the movement of the second frame. A timed relationship exists between the upward pivotal movement of the second frame and the pivotal movement of the drive arms such that linear movement of the carriage assembly means is momentarily suspended at the end of the printing stroke to eliminate ink drip and splatter. Shuttle means in the carriage assembly means engages stops at opposite ends of the support arms to shift the squeegee and the flood bar relative to one another by a novel parallelogram movement.

United States Patent 1191 Bubley et al.

[ 1 Jan. 14, 1975 SCREEN PRINTING PRESS [75] Inventors: Henry J. Bubley,Deerfield; Claude H. Oltra, Chicago, both of I11.

[73] Assignee: American Screen Printing Equipment Company, Chicago, Ill.

[22] Filed: Oct. 24, 1972 [21] Appl. No.: 299,689

Primary ExaminerRobert E. Bagwill Assistant ExaminerR. E. SuterAttorney, Agent, or Firm-Robert E. Wagner, Robert E. Brown; Stone,Wagner & Aubel [57] ABSTRACT An improved screen printing press having afirst frame with a surface to receive work for printing and a secondframe pivotally mounted on the first frame and having a pair ofspaced-apart support arms for movement therewith toward and away fromthe surface, a chase pivotally mounted on the first frame beneath thearms, and movable therewith, a screen removably mounted on the chase, acarriage assembly means, with a squeegee and a flood bar, mounted forrecipro- References Cited cal movement on the arms, the second framealso hav- UNITED STATES PATENTS ing, at a rear portion thereof, a pressdrive means op 1,821,302 9/1931 Gomer 101/126 eratively Connected todrive arms mounted for Pivotal 1,840,073 1/1932 Williams 101/123movement on the first frame to drive the Carriage 1,898,406 2/1933 Tateet al.... 101/123 sembly means. The second frame pivots with respect,989 10/1935 Wulf 101/126 to the first frame about an axis in the planeof the 2,704,510 3/1955 Walsh 101/123 work surface to eliminate smearingduring the move- 2,709,404 5/1955 Stokes 101/12 ment of the secondframe. A timed relationship exists I i u between the upward pivotalmovement of the second 2936705 5,1960 Z? esmanm W123 frame and thepivotal movement of the drive arms 2963964 12/1960 X such that linearmovement of the carriage assembly 219751705 3/1961 Gilman 101/123 meansis momentarily Suspended at the end of the 2,991,711 7/1961 Ehrhard 61a1 101/126 P g stroke to eliminate ink p and Splattee Shut- 3,605,6149/1971 Gilman etal...... 101/126 tle means in the carriage assemblymeans engages 3,731,623 5/1973 Bubley et. a1 101/123 X stops at oppositeends of the support arms to shift the FOREIGN PATENTS OR APPLICATIONSsqueegee and the flood bar relative to one another by 702 29s 3/1966Italy 101/123 3 novel parallelogram movement 17 Claims, 11 DrawingFigures PATENIEB JAN 1 4 I875 SHEEI 10F 3 SCREEN PRINTING PRESSBACKGROUND OF THE INVENTION This invention relates to screen printingapparatus in general and, more specifically, to a new and improvedstencil screen printing press designed to eliminate smearing of work andpermit easy scaling of the size of the press.

In known types of stencil screen printing apparatus, the printing head,including the screen frame, is raised and lowered to permit insertionand removal of the stock to be printed. In most previous printingapparatus, this printing head is mounted on a fixed frame containing'abed and press drive means, and is raised and lowered with respect to thebed and fixed frame on a pivot point above the bed. An advanced andnovel form of press of this type is sold by American Screen PrintingEquipment Company of Chicago, Ill. and is the subject of U.S. Ser. No.83,800, filed Oct. 26, 1970, and titled Glider Press, now U.S. Pat. No.3,731,623, issued May 8, 1973. Though this press contains many uniqueand desirable features, the printing head, when moved upwardly withrespect to the surface of the printing bed at the end of a print stroke,tends to move a rear portion of the screen into contact with the printedwork, because of the placement of the pivot point, thereby smearing thework.

This smearing problem was attempted to be solved by the prior art bypivoting the entire printing head and press drive means portion of theprinting press with respect to the fixed printing bed.

While it is believed that such construction will tend to eliminate thesmearing problem, the structure he teaches has several disadvantages.The pivot point in is disposed at the rearmost portion of the base,which places an inordinate amount of weight forward of the pivot point.This weight produces excessive stresses and wear on the power means andcam drive means, and instability and possible undesirable movement andvibration of the frame.

The prior art also mounts the driving arm, which drives the squeegee andflood bar assembly A, inside the support arms, on the pivoting frameitself. Since the assembly A is therefore movable with respect to amoving frame rather than a fixed frame or reference point, its movementand registration are adversely affected by any instability or movementof the movable frame. Because of these problems, it has been impossibleto engineer and construct large size printing presses according to Fuchsby merely scaling the size of the movable frame. The excessive weightand instability encountered have precluded proportioning elements suchas the drive arms necessary to scale the prior art to larger sizes.Finally, the prior art teaches pivoting the entire master frame aboutthe rear pivot point located slightly above the horizontal plane of thescreen, necessitating accurate re-registration of the entire frame andscreen, with respect to the printing surface, each time the printinghead moves downward.

DESCRIPTION OF THE INVENTION This invention provides an improved screenprinting press containing many features of U.S. Ser. No. 83,800, nowU.S. Pat. No. 3,731,623, mentioned above, while eliminating the problemsof smearing and splattering at the end of the printing cycle andpermitting scaling to any desirable size of press unit. U.S. Pat. No.3,731,623

was issued May 8, 1973 and assigned to American Screen Process EquipmentCompany, which is, by change of name, the same entity as the assignee ofthe present application. U.S. Pat. No. 3,731,623 is expresslyincorporatd in its entirety herein by reference thereto.

This improved screen printing press overcomes the disadvantages ofpresent presses by a first fixed frame and a second frame pivotal onpivot points disposed on the first frame in the horizontal planeof thesurface of the printing bed of the fixed frame, and in a vertical planeforward of the press drive means. The second frame supports the printinghead, including the support arms, the carriage assembly means having thesqueegee and flood bar, a chase and a screen frame mounted thereon, and,to the rear of the pivot points, a press drive means.

The location of the pivot point in the horizontal plane of the printingsurface allows movement of the printing head toward and away from theprinting surface with out smearing of the work since the chase andscreen will not move downwardly toward that surface when they arepivoted relative to the first frame with the printing head.

Another advantage of the present invention is that the drive arm meansconnecting the press drive means and the carriage assembly means aremounted on the first fixed frame and outside of the carriage assemblysupport arms. Such mounting assures steady and uniform movement of thecarriage assembly means by the drive arms since they are mounted on afixed reference point rather than a movable frame. It also allowssupport of the significant weight of the massive drive arms necessaryfor very large presses on the rigid first fixed frame rather than themovable second frame. This feature, together with the location of thepivot points on the first frame to permit a proper, balanceddistributionof the weight of the components mounted on the second frame on eitherside of the pivot point, allows sca ling of this press to any desiredsize by eliminating the stresses, excessive power demands and inordinateweight which precluded proportioning previous presses to larger sizes.

The novel relocation of the pivot point and the disposition of the armsdriving the carriage assembly means, did, unfortunately create a majorproblem. Near the end of the printing stroke, the printing head beginsto pivot with the second frame to an upward position off the press toallow removal of the printed work. At this point, the carriage assemblymeans would tend to creep and shake on the support arms, splattering inkon the printed work. This problem has been successfully overcome in thepresent invention, however, by a novel timed relationship between themovement of the printing head and the drive arms. To achieve thisrelationship, the press lift cam is so formed that, while it is beingrotated by the press drive means against a cam follower fixedly mountedon the first frame to move the printing head rapdily upward, theconnecting means driving the drive arm means, and being rotated at thesame speed of rotation by the same press drive means, will reach a pointof linear alignment in which, through a few degrees of rotation by thepress drive means, the slight relative movement of the connecting meanscauses only sufficient movement of the drive arm means to eliminateforward creep of the carriage assembly means. This programmed movementof the ward position, by itsconnection to the rigid drive arms,

for the brief period between the end of the print stroke and the fullupward movement of the head. This completely eliminates any shaking ofthe carriage assembly means andthe resulting spilling of ink.

The carriage assembly means itself has a novel parallelogram movementwhich acts to shift the flood bar and squeegee bar relative to oneanother while maintaining them in balanced, locked-in relationship.

The chase or master frame of this invention is independently pivotallymounted on a horizontal axis defined by the pivot points to permit theuse of either the harmonic peeling means set forth in detail in U.S.Ser. No. 83,800 now U.S. Pat. No. 3,731,623 or a uniform rate of peelwith this form of press so that off-contact printing resulting inhigh-fidelity prints is possible. The mounting of the chase in such amanner also permits accurate re-registration of the screen frame withrespect to the printing surface, since the chase will always remainregistered in the plane of the surface at its pivot point.

Accordingly, it is an object of this invention to provide an improvedscreen printing press which eliminates smearing of the work located onthe printing surface and which can be easily scaled to any desired size.

It is a further object of this invention to provide an improved, screenprinting press having drive arms mounted on a first fixed frame anddriven by a press drive mounted on a second frame pivotal on the firstframe about an axis in the plane of the printing surface, the movementof the second frame and the press drive arms being in a timedrelationship effective to control movement of the drive arms for adesired period of time at the end of a print stroke, while the secondframe is pivoted away from the printing bed, to eliminate smearing andsplattering of work.

It is still another object of this invention to provide an improvedscreen printing press in which the chase is independently pivotal aboutan axis between the pivot points of the second frame on the first frame,to insure accurate re-registration of the chase with respect to theprinting surfact.

It is also an object of this invention to provide an improved screenprinting press having a squeegee and flood bar mounted in balanced,locked-in relationship on a carriage assembly and shifted with respectto one another by a parallelogram movement.

These and other objects of this invention will become evident from thefollowing description of the drawings, illustrating a preferredembodiment wherein:

' FIG. 1 is a perspective view of the improved printing press of thisinvention shown with the printing head in its upward position near theend of a printing cycle;

, FIG. 2 is an enlarged, fragmentary side elevational view of theprinting press shown in FIG. 1 with the screen in printing'position;

FIGS. 3-7 are reduced side elevational views of the printing press shownin FIG. 1 which illustrate the operation of the press and the timedrelation between the movement of the second frame and the carriageassem- FIG. 8 is an end elevational view of the rear portion of thesecond frame including the power drive means, the cam, cam follower andsprings;

FIG. 9 is an enlarged fragmentary side elevational view of a carriageassembly positioned adjacent the forward stop means in the positionassumed during the print stroke;

FIG. 10 is an enlarged fragmentary side elevational view of the carriageassembly shown in FIG. 9 in the position assumed during the floodstroke; and,

FIG. 11 is a fragmentary side elevational view of the carriage assemblyshown in FIG. 10 converted to nonflood scoop position.

Referring now to the drawings, and in particular, to FIG. 1, theimproved screen printingpress of the present invention is showngenerally at 10. This press 10 includes a first fixed frame '12 having acontrol console 15 located at its front which permits an operator tocontrol the operation of the press. The first frame 12 has a printingbed 16 located at its top which is preferably a vacuum base of the typedescribed in now abandoned application U.S. Ser. No. 674,623, filed Oct.1 1, 1967 and titled Vacuum Base. A vacuumto the printing surface 17 ofbed 16 is supplied through a flexible conduit 19 joined to a vacuumsource 18, which is supported on the frame 12. The air flow through theconduit 19 may be reversed to provide a blow-black release of the stockbeing printed, which'is particularly advantageous in releasing heavystocks.

This screen printing press 10 also has a second frame 14 which ispivotally mounted on first frame 12 at a pivot point 13. The secondframe 14 is pivotally movable with respect to the first frame 12 on ahorizontal pivot shaft 23 extending between similar pivot points 13disposed on opposite sides of the first frame 12 and located inapproximately the samehorizontal plane as printing surface 17. Secondframel4 has, at its front portion, a screen printing head, indicatedgenerally at 20, which includes a pair of parallel spaced support arms21 and 21' having a carriage assembly means, generally indicated at 22,mounted for movement therealong.

The carriage assembly means 22 includes a carriage assembly 24 and 24'disposed on each of the support arms 21 and 21', respectively. Thecarriage assemblies 24 and 24 are of identical, but reverseconstruction, one being a mirror image of the other. They are linkedtogether for unitary movement by a pair of joining rods 30 extendingbetween them.

A master frame or chase 37 is disposed below support arms 21 and 21' andis mounted for independent pivotal movement about pivot shaft 23 on aspherical bearing 39 and a bracket 36 disposed on opposite sides offrame 12, as shown in FIG. 2. The master frame 37 is movably attachable,at its front end, to the midportion of a lateral brace 64 joined tovertical braces 65 and 65' which extend downwardly from support arms 21and 21' to assure rigidity of the chase 37. While this mounting enablesthe chase 37 to be raised with the printing head 20 during the printingcycle, it also permits the chase 37 to be lowered independently of thehead 20, for purposes of changing the stencil screen 38, by detachingits forward end from the lateral brace 64. Since the rear portion of thechase 37 will always, in this manner, be returned to its previousposition in the plane of the surface 17 of printing bed 16,

the problem of accurately re-registering the entire master frame uponchanging of the screen is eliminated.

The stencil screen, 38 is held in the chase 37 by clamps 68, or theequivalent, acting against its frame, which are chosen to facilitatereplacement of the screen. The entire printing head may be locked in tofront lock stops 90 and 90 during printing by bearings on braces 65 and65 to assure proper screen position.

The press drive means is mounted on a rearward portion of second frame14 and is generally indicated at 40 in FIG. 1 and shown in more detailin FIG. 8. It includes a motor 41 mounted on a movable motor support 42having a threaded shaft 43 cooperating with threads on the support topermit adjustment of the motor relative to the second frame 14. Avariable speed drive pulley 44 is mounted on motor 41 and, through abelt 45, drives a pulley 46 mounted on an inputshaft 47 of a reductiongear arrangement 48. The reduction arrangement 48 is of a known typehaving an output shaft 49 disposed at right angles to input shaft 47 andextending from its opposite sides. Output shaft 49 is rotated to drive apress lift cam 51 disposed on one side of gear arrangement 48 and a maindrive lever arm 50 disposed on the opposite side. A number ofmechanically operated switches and linkages 52 are coordinated andactivated with the operation of the press to perform various functionsin the printing cycle, e.g., energizing the vacuum bed and applying theblow-back. A take-off apparatus may be energized and synchronized withthe press by a microswitch mounted on the press. Clearly, additionalswitches could be provided for other accessories and the activation ofvarious functions could be accomplished by alternative means such aselectrical timers and switches and control cams.

The main drive lever arm 50 is connected, through a second arm 54, toL-shaped arm 55 which has its opposite end fixedly mounted on arotatable shaft 56 extending through bearings on the first frame 12 andjoined, at its opposite ends, to identical drive arms 59 and 59', asshown in FIG. 8.

The drive arms 59 and 59 which are mounted on the first frame 12 throughshaft 56, are generally L-shaped and connected at their opposite endsthrough drive rods 60 and 60 to carriage assemblies 24 and 24',respectively. As thedrive arms 59 and 59 are pivoted on frame 12 withshaft 56 by press drive 40, they act to drive carriage assemblies 24 and24' in forward and return strokes across bed 16 on arms 21 and 21. Thelength of stroke made by the drive arms and carriage assemblies isvariable by adjusting the position of second arm 54 in an arcuate slot57 formed in L-shaped arm 55, since shaft 56 and pivoting shaft 23 arealways maintained in vertical alignment and generally form a trianglewith output shaft 49.

The design of the press drive means 40 permits it to be located withinthe sides of the bed 17 and chase 37. As mentioned above, the mountingof the heavy drive arms 59 and 59 on the first frame 12 permits the sizeof the press to be proportionately increased without adverselyincreasing the weight of the second frame 14. Bed '17 is alsounobstructed by drive arms 59 and 59' during the printing cycle, whichpermits mechanical feeds, conveyors and the like to be used with thepress, or the press to be used as an element in a printing system. Wheremechanical-type takeoffs having mechanical fingers for removing printedstock from the press bed 17 are used, it has been found desirable toform cut-out areas in bed 17 along the edge of the press adjacent thetakeoff to permit the fingers to better grip the stock on the bed.

As shown in FIGS. 2 and 8, the press lift cam 51 is positioned so thatits perimeter is constantly in cooperation with a cam follower 62mounted on frame 12 through a rigid cam follower arm 63. As cam 51 isrotated on shaft 49 toward its high side, the second frame 14 is pivotedwith respect to the first frame 12 about pivot points 13 on pivot axis23, to move the printing head 20 upwardly away from the printing bed 16and the rear portion downwardly.

A carriage assembly 24 is described in more detail in FIGS. 9 and 10.This assembly is of identical, but reverse construction to carriageassembly 24 mounted on the opposite support arm 21. Carriage assembly 24has a housing 25 mounted on arm 21 and connected at its rearward end bya pivotal connection 27 to drive rod 60 and drive arm 59. Nylon guides(not shown) are provided within the housing 25 to assure smooth andfriction-free movement of the carriage assembly 24' along the arm 21,during the printing cycle. The housing 25 contains a shuttle 26 captivebetween its inside surface and the outside surface of arm 21. Theshuttle 26 is provided with a continuous cam track 31, which functionsto shfit a flood bar and a squeegee in a generally vertical movementrelative to one another. The shuttle 26 itself is linearly moved withrespect to housing 25 upon engaging stops 72 and 74 disposed at oppositeends of arm 21.

A shuttle catch 75 is pivotally mounted on housing 25 to engage shuttle26 and prevent its movement during the flood traverse. The catch isdisengaged when the shuttle hits stop 72. A movable parallelogramsupport 32 is disposed on the outside of housing 25 with the top andbottom members of the parallelogram pivotally mounted thereon throughbearing bolts 29. The opposite side members of the parallelogram 32 arepivotally connected to the top and bottom sides of the parallelogram 32to move in vertically opposite directions. One side member supports asqueegee assembly 33 and the other a flood bar assembly 35. A camfollower roller 28 is captively disposed to ride in cam track 31, and isattached through the vertical squeegee support member of theparallelogram to the squeegee assembly 33. This roller 28 functions tomove the parallelogram 32 in pivotal movement about the bearing bolts 29in response to linear movement of the shuttle 26 at the end of eachstroke. Thus, direct movement of the squeegee 33 with the roller 28causes corresponding opposite vertical movement of the flood bar 35,providing a system in which the squeegee and flood bar are positivelylocked in a constant relationship for corresponding movement.

At the end of the flood or return stroke, the stop 72 engages the facingend of shuttle 26 while the carriage housing 25 continues its transversemovement, thereby causing the cam follower roller 28 to be moved in thecam track 31, shifting the parallelogram 32 and Iowering the squeegee33, as shown in FIG. 9. At the opposite or rearward end of support arm21, the stop 74 engages the shuttle and shifts it in a similar manner toreverse the positions of the squeegee and flood bar, for the returnstroke, as shown in FIG. 10. In printing fabrics and the like, the floodbar and the flood bar assembly 35 may be replaced with a second squeegeeto permit printing in both directions. In such event, the cam 51 will betimed to lower the press head 20 before forward movement of the carriageassembly 40 is commenced.

Conversion of the press from'flood to non-flood condition can be rapidlyaccomplished with little effort, by release of the flood bar clamp 34,substitution of a nonflood scoop 80,and adjustment of the flood barassembly 35 by movement of shoulder screw 81 rearward and removal ofshoulder screw 82. Push arm 84 is then mounted on the rear of shuttle 26to'loca'te the nonflood scoop to cooperate with the squeegee on thereturn stroke. The simplicity of the mechanism assures proper non-floodand flood function at all times, since the parallelogram movementshifting the flood and squeegee assemblies is automatically actuated bythe shuttle at every change in direction of the press. With the chase 37in down position and the press head 20 elevated, the squeegee and theflood bar can be easily removed and cleaned or replaced.

The operation of the press is shown in FIGS. 1-7.

,When the press is in the condition shown in FIG. 1, the

stock to be printedmay be placed on the surface 17 of bed 16. The motor41 is then actuated through the central console causing the shaft torotate and the carriage assemblies 24 and 24' to be driven by the drivearms 59 and 59' to the front of the press, as shown in FIG. 2. Thecondition of each carriage assembly during the forward or non-printstroke is shown in FIG. 10 for the flood type operation. If a non-floodscoop is used, the position of the flood and squeegee assemblies wouldbe as shown in FIG. 11. In either operation, the ink' pool is moved tothe front of the screen by this stroke.

When the carriage ass e'mbly'means 22 reaches the end of the supportarms at the front of the press, the shuttles 26 and 26' are engaged bystops 72 and 72' lowering the squeegee assemblies and elevating theflood bar assemblies, as shown in-FIG. 3. At this point, as output shaft49 continues its rotation, the direction of the drive arms 59 and 59 isreversed. This occurs just as press lift cam 51 reaches its low side orsmallest radius so that the printing head is adjacent the printingsurface 17. The drive arms 59 and 59"continue to rotate with shaft 56 ina rearward direction to pull the squeegee across the stencil screen 38.In off-contact printing, as shaft 56 moves, a peeling mechanism, whichwill be explained below, functions to elevate the screen 38 behind thesqueegee. In on-contact printing, no elevation of the screen isexperienced.

FIG. 4 shows the press at approximately the midpoint of the printstroke, using the contact method in which the screen remains in place.When drive arms 59 and 59' reach the rear position, shown in FIG. 5, theprint stroke is complete. The carriage assemblies 24 and 24' haveengaged stops 74 and 74 near the rearof the respective press arms 21 and21', causing the flood bar to be lowered and the squeegee head to beelevated. At this point in time, the press lift cam 51 is approachingits high side, causing the second frame 14 to be pivoted abouthorizontal axis 23, thereby moving the printing head 20 away from theprinting bed 16.

FIGS. 5 and 6 clearly show the novel, timed relationship between themovement of the second frame 14 and the movementof the drive arms 59 and59' and associated carriage assembly means 22. As shown in thesefigures, the second frame 14 continues to be pivoted and the printinghead 20 raised to its uppermost position, while the drive arms arebackedoff slightly to hold carriage assembly means 22 in a positionadjacent stops 74 and 74' thereby preventing forward creep along thepress arms. While cam 51 moves to its greatest radius, main drive leverarm 50 and the second arm 54 move through an arc which imparts onlysufficient rearward linear movement to the drive arms 59 and 59 toconstantly maintain carriage assembly means 22 adjacent the rear of thepress arms during the continuing upward movement of the printing head.Since carriage assembly means 22 is therefore held firmly adjacent stops74 and 74' by this slight, but constant backing off force of the drivearms exactly corresponding to the movement of the printing head andtheforward force exerted by the press arms on the carriage assemblymeans, shaking or vibration and splattering of ink is eliminated. It isalso significant that because of the lo cation of pivot point 13, therear portion of screen 38 never swings in an are that will bring it incontact with the surface 17 of the printing bed 16. The entire press mayalso be caused to dwell or stop in the condition shown in FIG. 6 toenable the removal of printed stock and the insertion of unprintedstock.

As shaft 49 continues to rotate cam 51 and lever arm 50, the secondframe 14 begins to pivot toward the printing surface 17, and lever arm50 and second arm 54 reach a point in their arc where their movementinitiates forward movement of the drive arms 59 and 59' and the carriageassembly means 22, as shown in FIG. 7. The second frame 14 is also beingconstantly urged to a horizontal position with respect to the printingbed 16 of the first frame 12 by spring means 58 and 58' which have oneend connected by a turnbuckle to a rear portion of the second frame l4and an opposite end connected to a supporting brace on the first fixedframe 12.

In many types of screen printing, particularly when using a screenmaterial that has appreciable stretch, it is desirable to useoff-contact printing. This type of printing is achieved by lifting orpeeling the stencil screen behind the squeegee as the squeegee is movedalong the support arms in the print stroke. This peeling of the stencilscreen may be accomplished, in the present invention, by a peelingmechanism which is not shown herein but which is similar to thatdescribed in US. Ser. No. 83.800, filed Oct. 26, I970 and titled GliderPress now US. Pat. No. 3,731,623, which is incorporated in its entiretyherein by reference thereto. The peeling mechanism disclosed in thatapplication may be mounted on the present press so that the rate ofpeeling follows a harmonic motion pattern in that peeling is faster asthe squeegee moves across the center of the screemthan at either end,thereby compensating for the greater tendency of the screen materials tostretch at that point. Peeling is accomplished by cables connected tothe front of chase 37 and releasable therefrom to permit movement of thechase with respect to the printing head 20. These cables are eachextended over pulleys and through a support arm 21 or 21' to pulleyspositioned on shaft 56 for rotation therewith. As shaft 56 rotates inresponse to movement of L-shaped arm 55, a pulling force is exerted onthe cables, lifting the chase in opposition to the downward pressure ofthe sequeegee assembly on the stencil screen. When metallic or otherscreen material having little appreciable stretch is used, off-contactprinting may also be satisfactorily accomplished with this invention byuse of a uniform rate of peeling means. An alternative form of peelingmeans linkage to that described above which may be used to performeither harmonic or uniform peeling is operated directly from a peelingcam being rotated by shaft 49. As the peeling cam rotates, it moves alever arm pivotally mounted on the second frame 14. The disposition ofthe peeling cables is as described above except that one end of thecable is attached near the end of the lever arm opposite its pivotpoint. The point of attachment of the cable to the lever arm may beadjusted along the lever arm to vary the amount of peel. The rate ofpeel, from uniform to harmonic, can be adjusted by changing the shape ofthe cam as necessary.

The press of the present invention is of rugged design and constructedof standard, available materials, which makes it quite economical tomanufacture. Moreover, the press is of universal design, permitting itto be scaled up or down to meet particular customer requirements. Uponconsideration of the foregoing, it will become obvious to those skilledin the art that various modifications may be made without departing fromthe invention embodied herein. Therefore, only such limitations shouldbe imposed as are indicated by the spirit and scope of the appendedclaims.

We claim:

1. A printing press, including fixed frame, a bed supported on saidframe and having an upwardly facing surface to receive work to beprinted, a second frame pivotally mounted on said first frame, a pair ofspacedapart arms mounted on a front portion of said second frame forpivotal movement therewith toward and away from said bed, a chasepivotally mounted beneath said arms, said chase being positioned oversaid work on said bed during printing, a screen removably mounted onsaid chase, carriage assembly means mounted on said arms for movementtherealong, a drive arm pivotally mounted on said first frame andconnected to said carriage assembly means, press drive means mountedentirely on a rear portion of said second movable frame to move saidcarriage assembly means reciprocally along said arms during a printingcycle and to pivot said second movable frame relative to said firstfixed frame during the printing cycle, means operatively connecting saidpress drive means mounted on said second frame to said drive arm meanspivotally mounted on said first frame, said press drive meansoperatively engaging said first frame to pivotally move said secondframe about a pivot point disposed generally in the horizontal plane ofsaid surface of said bed adjacent a rear edge of said surface andallowing said rear portion of said second frame on which said pressdrive means is mounted to be swung below said horizontal plane of saidsurface of said bed during the printing cycle, such positioning of saidpivot point thereby eliminating smearing of work placed on said bed, bypreventing any portion of said screen from contacting said work to beprinted during movement of said second frame during a printing cycle,said press drive means moving said second movable frame and said drivearm relative to one another during said printing cycle such that, for adesired period of time, the disposition of said means connecting saidpress drive means to said drive arm causes said carriage assembly meansto be maintained adjacent a selected point along said arms during theupward movement of said second frame to thereby eliminate creep of saidcarriage assembly means along said arms and resulting dripping of ink.

2. The printing apparatus of claim 1 wherein said second frame is urgedtoward a horizontal position with respect to said first frame such thatsaid screen and said bed lie in parallel planes, by resilient meansjoining said rear portion of said second frame to said first frame.

3. The printing press of claim 1 wherein said press drive means includesa power drive shaft rotatable about a central axis, said power driveshaft having a cam mounted for rotation therewith near one end thereofand linking means mounted'on an opposite end thereof and operativelyconnecting said press drive means with said drive arm to pivot saiddrive arm relative to said first frame, said cam engaging a cam followermounted on said first frame to move said second frame about said pivotpoint, said cam and said linking means being moved by said power driveshaft driven by said press drive means, such that as the rotation ofsaid cam causes said second frame to be pivoted upward with respect tosaid bed near the end of a printing stroke, further movement of saidlinking means will, through a desired period of time, cause sufficientbacking movement of said drive arm and said connected carriage assemblyto preclude forward creep of said carriage assembly along saidspaced-apart arms during said upward movement of said second frame.

4. The printing press of claim 1 wherein said drive arm mounted on saidfirst frame includes a pair of spaced drive arms mounted forcorresponding pivotal movement with respect to said first frame on adrive shaft extending between them, each of said drive arms disposedoutside of said arms supporting said carriage assembly.

5. The printing press of claim 1 wherein said chase is mounted on ahorizontal axis defined by said pivot points on said first frame and isindependently pivotal about said axis to allow peeling of said screenduring the printing cycle, while always having a portion thereofmaintained in proper registered relation to said bed to facilitateregistration of said chase with respect to said bed and said firstframe.

6. The printing press of claim 1 wherein said bed has a plurality ofcut-out portions formed along one edge thereof to facilitate access towork positioned on said bed to allow its gripping, removal and transfer.

7. A printing press including a first fixed frame, a bed supported onsaid frame and having an upwardly facing surface to receive work to beprinted, a second frame pivotally mounted on said first frame, a pair ofspacedapart arms mounted on a front portion of said second frame forpivotal movement therewith toward and away from said bed, a chasepivotally mounted beneath said arms, said chase being positioned oversaid work on said bed during printing, a screen removably mounted onsaid chase, a carriage assembly mounted on said arms for movementtherealong, a drive arm pivotally mounted on said first frame andconnected to said carriage assembly, press drive means mounted on a rearportion of said second frame and operatively connected to said drive armto drive said drive arm and thereby move said carriage assemblyreciprocally along said arms, said press drive means including a powerdrive shaft rotatable about a central axis, said power drive shafthaving a cam mounted for rotation therewith near one end thereof andlinking means mounted on an opposite end thereof and operativelyconnecting said press drive means with said drive arm to pivot saiddrive arm relative to said first frame, said second frame beingpivotally moved by said press drive means with respect to said firstframe during a printing cycle about a pivot point disposed generally inthe horizontal plane of said surface of said bed adjacent a rear edge ofsaid surface and allowing saidrear portion of said second frame on whichsaid press drive means is mounted to be swung below said horizontalplane of said surface of said bed during the printing cycle, saidlinking means including a press drive arm fixedly mounted on said powerdrive shaft for rotation therewith, a rod pivotally connected at one endto an outward end of said press drive arm and moved in generallyreciprocal movement thereby, an L-shaped slot arm fixedly mounted nearone end thereof on a shaft, said shaft pivotally mounted on said firstframe and having said drive arm connected thereto, said slot arm beingadjustably connected near its opposite end to said rod, said camengaging a cam follower mounted on said first frame to move said secondframe about said pivot point, said cam including a press lift cam havinga varying radius, said cam and said linking means being moved by saidpower drive shaft driven by said press drive means to cause a relatedmovement of said second frame and said drive arm sufficient to preventcreep of said carriage assembly on said arms while said second framecontinues to pivot upward when said press drive arm sweeps through anarc bridging the lowest point on its circle of rotation whilesaid presslift cam engages said cam follower across the greatest radius of saidcam.

8. A printing press, including a first fixed frame, a bed supported onsaid frame and having an upwardly facing surface to receive work to beprinted, a second frame pivotally mounted on said first frame, a pair ofspaced-apart arms mounted on a front portion of said second frame forpivotal movement therewith toward and away from said bed, a chasepivotally mounted be neath said arms, said chase being positioned oversaid work on said bed during printing, a screen removably mounted onsaid chase, a carriage assembly mounted on said arms for movementtherealong, a drive arm pivotally mounted on said first frame andconnected to said carriage assembly, press drive means mounted on a rearportion of said second frame and operatively connected to said drive armto drive said drive arm and thereby move said carriage assemblyreciprocally along said arms, said carriage assembly including a pair ofspaced carriage housings, each housing supported on one-of said arms,means on each carriage housing for supporting a squeegee and a flood barin associated relationship for movement relative to each othercorresponding to the position of said screen over said bed, saidsqueegee being brought into contact with said screen when said screen ispositioned over said work, and means for shifting said squeegee and saidflood bar relative to each other to automatically and properly positionthe same during movement of said carriage housings on said arms, saidsecond frame being pivotally moved by said press drive means withrespect to said first frame during a printing cycle about a pivot pointdisposed generally in the horizontal plane of said surface of said bedadjacent a rear edge of said surface and allowing said rear portion ofsaid second frame on which said press drive means is mounted to be swungbelow said horizontal plane of said surface of said bed during theprinting cycle, such positioning of said pivot point thereby eliminatingsmearing of work placed on said bed, by preventing any portion of saidscreen from contacting said work to be printed during movement of saidsecond frame during a printing cycle, the operative relationship betweenthe pivotal movement of said second frame and the movement of said drivearm by said press drive means being such that said carriage housings aremaintained at selected points along said arms with said cam track insaid shuttle and stop means disposed near opposite ends of each of saidarms to engage and reversibly" move said shuttle as said carriageassembly is moved adjacent each end of said arms, the movement of saidshuttle by said stop means operating to pivot said means supporting saidsqueegee and flood bar to shift said squeegee and said flood bar in agenerally vertical direction relative to each other.

9. In a printing press having a first fixed frame, a bed supported onsaid frame having an upwardly facing surface to receive work to beprinted, a second frame mounted for pivotal movement on said firstframe, a pair of spacedapart arms mounted on said second frame formovement therewith, a chase pivotally mounted beneath said arms andpositioned over said work on said bed during printing, a screenremovably mounted on said chase, a carriage assemblymounted on each ofsaid arms for movement therealong, a drive arm connected to each of saidcarriage assemblies, press drive means mounted on said second frame andoperatively connected to each drive arm to drive each drive arm andthereby move each of said carriage assemblies in associated, reciprocalfashion along said arms, the improvements including pivot pointsdisposed on opposite sides of said first frame and forming a horizontalaxis about which said second frame is pivotally moved during a printingcycle, said pivot points disposed generally in the horizontal plane ofsaid surface of said bed adjacent a rear edge of said surface andallowing a rear portion of said second frame on which said press drivemeans is mounted to be swung below said horizontal plane of said surfaceof said bed during the printing cycle to prevent smearing contactbetween said screen and said work on said bed by never allowing anyportion of said screen to move below the horizontal plane of said pivotpoints during movement of said second frame, said press drive meansbeing mounted entirely on said rear portion of said second movable frameto move said carriage assemblies reciprocally along said arms during aprinting cycle, and to pivot said second movable frame relative to saidfirst fixed frame during the printing cycle, means operativelyconnecting said press drive means mounted on said second frame to saiddrive arms pivotally mounted on said first frame, said press drive meansoperatively engaging said first frame to pivotally move said secondframe about said pivot points during the printing cycle, said pressdrive means moving said second movable frame and said drive armsrelative to one another during the printing cycle, such that, for adesired period of time, the disposition of said means connecting saidpress drive 13 means to said drive arms causes said carriage assembliesto be maintained adjacent a selected point along said arms during saidupward movement of said second frame to eliminate dripping of ink onsaid work.

10. The printing press of claim 9 wherein said press drive meansincludes a power drive shaft rotatable about a central axis, said powerdrive shaft having a cam mounted for rotation therewith near one endthereof and linking means mounted on an opposite end thereof andoperatively connecting said press drive means with said drive arms topivot said drive arms relative to said first frame, said cam engaging acam fol lower mounted on said first frame to move said second frameabout said pivot point, said cam and said linking means being moved bysaid power drive shaft driven by said press drive means, such that asthe rotation of said cam causes said second frame to be pivoted upwardwith respect to said bed near the end of a printing stroke, furthermovement of said linking means will, through a desired period of time,cause sufficient backing movement of said drive arms and said connectedcarriage assemblies to preclude forward creep of said carriageassemblies along said spaced-apart arms during said upward movement ofsaid second frame.

11. The improvement set forth in claim 9 wherein said drive arm includesa pair of spaced-apart L-shaped arms pivotally mounted on said firstfixed frame within the side margins of said chase, said L-shaped armsbeing mounted on a common axis which is in generally vertical alignmentwith the horizontal axis between said pivot points of said second frameon said first frame.

12. The improvement set forth in claim 9 wherein said press drive meansincludes a power drive shaft rotatable about a central axis andadjustable linkage means to impart motion from said power drive shaft toeach drive arm to drive said carriage assemblies reciprocally along saidarms, said central axis of said power drive shaft, said axis ofsaidpivot points and an axis extending between said drive arms generallyforming a triangulate prismatic arrangement during the printing cycle,to permit adjustment of the length of the stroke of said carriageassemblies by adjustment of said linkage means connecting said driveshaft and said axis extending between said drive arms.

13. The improvement set forth in claim 9 wherein said chase is mountedon said horizontal axis defined by said pivot points on said first frameand is independently pivotal about said axis to allow peeling of saidscreen during the printing cycle, while always having a portion thereofmaintained in proper registered relation to said bed to facilitateregistration of said chase with respect to said bed and said firstframe.

14. In a printing press having a first fixed frame, a bed supported onsaid frame having an upwardly facing surface to receive work to beprinted, a second frame mounted for pivotal movement on said firstframe, a pair of spaced-apart arms mounted on said second frame formovement therewith, a chase pivotally mounted beneath said arms andpositioned over said work on said bed during printing a screen removablymounted on said chase, a carriage assembly mounted on each of said armsfor movement therealong, a drive arm connected to each of said carriageassemblies, press drive means mounted on said second frame andoperatively connected to each drive arm to drive each drive arm andthereby move each of said carriage assemblies in associated, reciprocalfashion along said arms, said press drive means including a power driveshaft rotatable about a central axis, said power drive shaft having acam mounted for rotation therewith near one end thereof and linkingmeans mounted on an opposite end thereof and operatively connecting saidpress drive means with said drive arms to pivot said drive arms relativeto said first frame, the improvements including pivot points disposed onopposite sides of said first frame and forming a horizontal axis aboutwhich said second frame is pivotally moved during a printing cycle, saidpivot points disposed generally in the horizontal plane of said surfaceof said bed adjacent a rear edge of said surface and allowing a rearportion of said second frame on which said press drive means is mountedto be swung below said horizontal plane of said surface of said bedduring the printing cycle, said linking means including a press drivearm fixedly mounted on said power drive shaft for rotation therewith, arod pivotally connected at one end to an outward end of said press drivearm and moved in generally reciprocal movement thereby, an L-shaped slotarm fixedly mounted near one end thereof on a shaft, said shaftpivotally mounted on said first frame and having each drive armconnected thereto, each slot arm being adjustably connected near itsopposite end to said rod, said cam engaging a cam follower mounted onsaid first frame to pivotally'move said second frame about said pivotpoint, said cam including a press lift cam having a varying radius, saidcam and said linking means being moved by said power drive shaft drivenby said press drive means to cause a related movement of said secondframe and said drive arms sufficient to prevent creep of said carriageassemblies on said arms while said second frame continues to pivotupward when said press drive arm sweeps through an arc bridging thelowest point on its circle of rotation while said press lift cam engagessaid cam follower across the greatest radius of said cam.

15. in a printing press having a first fixed frame, a bed supported onsaid frame having an upwardly facing surface to receive work to beprinted, a second frame mounted for pivotal movement on said firstframe, a pair of spaced-apart arms mounted on said second frame formovement therewith, a chase pivotally mounted beneath said arms andpositioned over said work on said bed during printing, a screenremovably mounted on said chase, a carriage assembly mounted on each ofsaid arms for movement therealong, a drive arm connected to each of saidcarriage assemblies, press drive means mounted on said second frame andoperatively connected to each drive arm to drive each drive arm andthereby move each of said carriage assemblies in associated, reciprocalfashion along said arms, the improvements including pivot pointsdisposed on opposite sides of said first frame and forming a horizontalaxis about which said second frame is pivotally moved during a printingcycle, said pivot points disposed generally in the horizontal plane ofsaid surface of said bed adjacent a rear edge of said surface andallowing a rear portion of said second frame on which said press drivemeans is mounted to be swung below said horizontal plane of said surfaceof said bed during the printing cycle to prevent smearing contactbetween said screen and said work on said bed by never allowing anyportion of said screen to move below the horizontal plane of said pivotpoints during movement of said second frame, and each drive arm beingpivotally mounted on said first fixed frame and being driven by saidpress drive means in an operative, synchronized relationship to themovement of said second frame upward with respect to said bed such thatsaid carriage assemblies are maintained adjacent a selected point alongsaid arms during said upward movement of said second frame to eliminatedripping of ink on said work, each of said carriage assemblies includinga carriage housing movably mounted on each of said arms, said drive armbeing connected to each carriage housing to reciprocally move eachcarriage housing along said arms during the printing cycle, meanspivotally mounted on each carriage housing for supporting a squeegee anda flood bar in associated relationship for movement relative to eachother corresponding to the movement of said.

tion the same during movement of said carriage assemblies on said arms.

16. A printing press including a first fixed frame, a bed supported onsaid frame and having an upwardly facing surface to receive work to beprinted, a second frame pivotally mounted on said first frame, a pair ofspaced-apart arms mounted on said second frame for pivotal movementtherewith toward and away from said bed, a chase pivotally mountedbeneath said arms and positioned over said work on said bed duringprinting, a screen removably mounted on said chase, a carriage assemblymounted on each of said arms for movement therealong, each of saidcarriage assemblies having a carriage housing supported on said arm,parallelogram means pivotally mounted on each carriage housing forsupporting a squeegee and a flood bar in associated relationship forpivoting movement relative to each other, a free sliding shuttlecontained in each carriage housing and movable with respect thereto,said shuttle operatively connected to said parallelogram means to pivotsaid parallelogram means to shift said squeegee and said flood bargenerally vertically with respect to one another upon movement of saidshuttle relative to said carriage housing, drive arms pivotally mountedon said first frame and connected to each of said carriage housings,press drive means mounted on said second frame and operatively connectedto said drive arms to drive said drive arms and thereby move saidcarriage assemblies reciprocally along said arms, and stops disposednear opposite ends of each of said arms to engage opposite ends of saidshuttle when-said carriage assemblies are moved adjacent said stops andmove said shuttle within each carriage housing to shift said squeegeeand said flood bar relative to each other, the operative relationshipbetween the pivotal movement of said second frame and the movement ofsaid drive arms being such that said carriage assemblies are maintainedadjacent said stops following a printing stroke for a desired period fortime while said second frame is being pivoted on said first frame upwardfrom said bed thereby to eliminate creep of said carriage assembliesalong said arms and resulting dripping of ink upon said work.

17. The printing press set forth in claim 16 wherein a first member ofsaid parallelogram means may be moved with respect to a second member ofsaid parallelogram'and maintained in position by a push arm means toconvert each carriage assembly to a non-flood scoop printing operation.

1. A printing press, including fixed frame, a bed supported on saidframe and having an upwardly facing surface to receive work to beprinted, a second frame pivotally mounted on said first frame, a pair ofspaced-apart arms mounted on a front portion of said second frame forpivotal movement therewith toward and away from said bed, a chasepivotally moUnted beneath said arms, said chase being positioned oversaid work on said bed during printing, a screen removably mounted onsaid chase, carriage assembly means mounted on said arms for movementtherealong, a drive arm pivotally mounted on said first frame andconnected to said carriage assembly means, press drive means mountedentirely on a rear portion of said second movable frame to move saidcarriage assembly means reciprocally along said arms during a printingcycle and to pivot said second movable frame relative to said firstfixed frame during the printing cycle, means operatively connecting saidpress drive means mounted on said second frame to said drive arm meanspivotally mounted on said first frame, said press drive meansoperatively engaging said first frame to pivotally move said secondframe about a pivot point disposed generally in the horizontal plane ofsaid surface of said bed adjacent a rear edge of said surface andallowing said rear portion of said second frame on which said pressdrive means is mounted to be swung below said horizontal plane of saidsurface of said bed during the printing cycle, such positioning of saidpivot point thereby eliminating smearing of work placed on said bed, bypreventing any portion of said screen from contacting said work to beprinted during movement of said second frame during a printing cycle,said press drive means moving said second movable frame and said drivearm relative to one another during said printing cycle such that, for adesired period of time, the disposition of said means connecting saidpress drive means to said drive arm causes said carriage assembly meansto be maintained adjacent a selected point along said arms during theupward movement of said second frame to thereby eliminate creep of saidcarriage assembly means along said arms and resulting dripping of ink.2. The printing apparatus of claim 1 wherein said second frame is urgedtoward a horizontal position with respect to said first frame such thatsaid screen and said bed lie in parallel planes, by resilient meansjoining said rear portion of said second frame to said first frame. 3.The printing press of claim 1 wherein said press drive means includes apower drive shaft rotatable about a central axis, said power drive shafthaving a cam mounted for rotation therewith near one end thereof andlinking means mounted on an opposite end thereof and operativelyconnecting said press drive means with said drive arm to pivot saiddrive arm relative to said first frame, said cam engaging a cam followermounted on said first frame to move said second frame about said pivotpoint, said cam and said linking means being moved by said power driveshaft driven by said press drive means, such that as the rotation ofsaid cam causes said second frame to be pivoted upward with respect tosaid bed near the end of a printing stroke, further movement of saidlinking means will, through a desired period of time, cause sufficientbacking movement of said drive arm and said connected carriage assemblyto preclude forward creep of said carriage assembly along saidspaced-apart arms during said upward movement of said second frame. 4.The printing press of claim 1 wherein said drive arm mounted on saidfirst frame includes a pair of spaced drive arms mounted forcorresponding pivotal movement with respect to said first frame on adrive shaft extending between them, each of said drive arms disposedoutside of said arms supporting said carriage assembly.
 5. The printingpress of claim 1 wherein said chase is mounted on a horizontal axisdefined by said pivot points on said first frame and is independentlypivotal about said axis to allow peeling of said screen during theprinting cycle, while always having a portion thereof maintained inproper registered relation to said bed to facilitate registration ofsaid chase with respect to said bed and said first frame.
 6. Theprinting press of claim 1 wherein said bed has a plurality of cut-outportions formed along one edge thereof to facilitate access to workpositioned on said bed to allow its gripping, removal and transfer.
 7. Aprinting press including a first fixed frame, a bed supported on saidframe and having an upwardly facing surface to receive work to beprinted, a second frame pivotally mounted on said first frame, a pair ofspaced-apart arms mounted on a front portion of said second frame forpivotal movement therewith toward and away from said bed, a chasepivotally mounted beneath said arms, said chase being positioned oversaid work on said bed during printing, a screen removably mounted onsaid chase, a carriage assembly mounted on said arms for movementtherealong, a drive arm pivotally mounted on said first frame andconnected to said carriage assembly, press drive means mounted on a rearportion of said second frame and operatively connected to said drive armto drive said drive arm and thereby move said carriage assemblyreciprocally along said arms, said press drive means including a powerdrive shaft rotatable about a central axis, said power drive shafthaving a cam mounted for rotation therewith near one end thereof andlinking means mounted on an opposite end thereof and operativelyconnecting said press drive means with said drive arm to pivot saiddrive arm relative to said first frame, said second frame beingpivotally moved by said press drive means with respect to said firstframe during a printing cycle about a pivot point disposed generally inthe horizontal plane of said surface of said bed adjacent a rear edge ofsaid surface and allowing said rear portion of said second frame onwhich said press drive means is mounted to be swung below saidhorizontal plane of said surface of said bed during the printing cycle,said linking means including a press drive arm fixedly mounted on saidpower drive shaft for rotation therewith, a rod pivotally connected atone end to an outward end of said press drive arm and moved in generallyreciprocal movement thereby, an L-shaped slot arm fixedly mounted nearone end thereof on a shaft, said shaft pivotally mounted on said firstframe and having said drive arm connected thereto, said slot arm beingadjustably connected near its opposite end to said rod, said camengaging a cam follower mounted on said first frame to move said secondframe about said pivot point, said cam including a press lift cam havinga varying radius, said cam and said linking means being moved by saidpower drive shaft driven by said press drive means to cause a relatedmovement of said second frame and said drive arm sufficient to preventcreep of said carriage assembly on said arms while said second framecontinues to pivot upward when said press drive arm sweeps through anarc bridging the lowest point on its circle of rotation while said presslift cam engages said cam follower across the greatest radius of saidcam.
 8. A printing press, including a first fixed frame, a bed supportedon said frame and having an upwardly facing surface to receive work tobe printed, a second frame pivotally mounted on said first frame, a pairof spaced-apart arms mounted on a front portion of said second frame forpivotal movement therewith toward and away from said bed, a chasepivotally mounted beneath said arms, said chase being positioned oversaid work on said bed during printing, a screen removably mounted onsaid chase, a carriage assembly mounted on said arms for movementtherealong, a drive arm pivotally mounted on said first frame andconnected to said carriage assembly, press drive means mounted on a rearportion of said second frame and operatively connected to said drive armto drive said drive arm and thereby move said carriage assemblyreciprocally along said arms, said carriage assembly including a pair ofspaced carriage housings, each housing supported on one of said arms,means on each carriage housing for supporting a squeegee and a flood barin associated relationship for movement relative to each othercorrespondinG to the position of said screen over said bed, saidsqueegee being brought into contact with said screen when said screen ispositioned over said work, and means for shifting said squeegee and saidflood bar relative to each other to automatically and properly positionthe same during movement of said carriage housings on said arms, saidsecond frame being pivotally moved by said press drive means withrespect to said first frame during a printing cycle about a pivot pointdisposed generally in the horizontal plane of said surface of said bedadjacent a rear edge of said surface and allowing said rear portion ofsaid second frame on which said press drive means is mounted to be swungbelow said horizontal plane of said surface of said bed during theprinting cycle, such positioning of said pivot point thereby eliminatingsmearing of work placed on said bed, by preventing any portion of saidscreen from contacting said work to be printed during movement of saidsecond frame during a printing cycle, the operative relationship betweenthe pivotal movement of said second frame and the movement of said drivearm by said press drive means being such that said carriage housings aremaintained at selected points along said arms during upward movement ofsaid second frame to thereby preclude creeping of said carriage housingsalong said arms and thereby eliminate dripping of ink on said work, saidmeans for shifting said squeegee and said flood bar including a shuttlecontained within each carriage housing and having a cam track formedtherein, a cam follower mounted on said means for supporting saidsqueegee and flood bar and cooperating with said cam track in saidshuttle and stop means disposed near opposite ends of each of said armsto engage and reversibly move said shuttle as said carriage assembly ismoved adjacent each end of said arms, the movement of said shuttle bysaid stop means operating to pivot said means supporting said squeegeeand flood bar to shift said squeegee and said flood bar in a generallyvertical direction relative to each other.
 9. In a printing press havinga first fixed frame, a bed supported on said frame having an upwardlyfacing surface to receive work to be printed, a second frame mounted forpivotal movement on said first frame, a pair of spaced-apart armsmounted on said second frame for movement therewith, a chase pivotallymounted beneath said arms and positioned over said work on said bedduring printing, a screen removably mounted on said chase, a carriageassembly mounted on each of said arms for movement therealong, a drivearm connected to each of said carriage assemblies, press drive meansmounted on said second frame and operatively connected to each drive armto drive each drive arm and thereby move each of said carriageassemblies in associated, reciprocal fashion along said arms, theimprovements including pivot points disposed on opposite sides of saidfirst frame and forming a horizontal axis about which said second frameis pivotally moved during a printing cycle, said pivot points disposedgenerally in the horizontal plane of said surface of said bed adjacent arear edge of said surface and allowing a rear portion of said secondframe on which said press drive means is mounted to be swung below saidhorizontal plane of said surface of said bed during the printing cycleto prevent smearing contact between said screen and said work on saidbed by never allowing any portion of said screen to move below thehorizontal plane of said pivot points during movement of said secondframe, said press drive means being mounted entirely on said rearportion of said second movable frame to move said carriage assembliesreciprocally along said arms during a printing cycle, and to pivot saidsecond movable frame relative to said first fixed frame during theprinting cycle, means operatively connecting said press drive meansmounted on said second frame to said drive arms pivotally mounted onsaid first frame, said press drive means operatively Engaging said firstframe to pivotally move said second frame about said pivot points duringthe printing cycle, said press drive means moving said second movableframe and said drive arms relative to one another during the printingcycle, such that, for a desired period of time, the disposition of saidmeans connecting said press drive means to said drive arms causes saidcarriage assemblies to be maintained adjacent a selected point alongsaid arms during said upward movement of said second frame to eliminatedripping of ink on said work.
 10. The printing press of claim 9 whereinsaid press drive means includes a power drive shaft rotatable about acentral axis, said power drive shaft having a cam mounted for rotationtherewith near one end thereof and linking means mounted on an oppositeend thereof and operatively connecting said press drive means with saiddrive arms to pivot said drive arms relative to said first frame, saidcam engaging a cam follower mounted on said first frame to move saidsecond frame about said pivot point, said cam and said linking meansbeing moved by said power drive shaft driven by said press drive means,such that as the rotation of said cam causes said second frame to bepivoted upward with respect to said bed near the end of a printingstroke, further movement of said linking means will, through a desiredperiod of time, cause sufficient backing movement of said drive arms andsaid connected carriage assemblies to preclude forward creep of saidcarriage assemblies along said spaced-apart arms during said upwardmovement of said second frame.
 11. The improvement set forth in claim 9wherein said drive arm includes a pair of spaced-apart L-shaped armspivotally mounted on said first fixed frame within the side margins ofsaid chase, said L-shaped arms being mounted on a common axis which isin generally vertical alignment with the horizontal axis between saidpivot points of said second frame on said first frame.
 12. Theimprovement set forth in claim 9 wherein said press drive means includesa power drive shaft rotatable about a central axis and adjustablelinkage means to impart motion from said power drive shaft to each drivearm to drive said carriage assemblies reciprocally along said arms, saidcentral axis of said power drive shaft, said axis of said pivot pointsand an axis extending between said drive arms generally forming atriangulate prismatic arrangement during the printing cycle, to permitadjustment of the length of the stroke of said carriage assemblies byadjustment of said linkage means connecting said drive shaft and saidaxis extending between said drive arms.
 13. The improvement set forth inclaim 9 wherein said chase is mounted on said horizontal axis defined bysaid pivot points on said first frame and is independently pivotal aboutsaid axis to allow peeling of said screen during the printing cycle,while always having a portion thereof maintained in proper registeredrelation to said bed to facilitate registration of said chase withrespect to said bed and said first frame.
 14. In a printing press havinga first fixed frame, a bed supported on said frame having an upwardlyfacing surface to receive work to be printed, a second frame mounted forpivotal movement on said first frame, a pair of spaced-apart armsmounted on said second frame for movement therewith, a chase pivotallymounted beneath said arms and positioned over said work on said bedduring printing a screen removably mounted on said chase, a carriageassembly mounted on each of said arms for movement therealong, a drivearm connected to each of said carriage assemblies, press drive meansmounted on said second frame and operatively connected to each drive armto drive each drive arm and thereby move each of said carriageassemblies in associated, reciprocal fashion along said arms, said pressdrive means including a power drive shaft rotatable about a centralaxis, said power drive shaft having a cam mounted for rotation therewiThnear one end thereof and linking means mounted on an opposite endthereof and operatively connecting said press drive means with saiddrive arms to pivot said drive arms relative to said first frame, theimprovements including pivot points disposed on opposite sides of saidfirst frame and forming a horizontal axis about which said second frameis pivotally moved during a printing cycle, said pivot points disposedgenerally in the horizontal plane of said surface of said bed adjacent arear edge of said surface and allowing a rear portion of said secondframe on which said press drive means is mounted to be swung below saidhorizontal plane of said surface of said bed during the printing cycle,said linking means including a press drive arm fixedly mounted on saidpower drive shaft for rotation therewith, a rod pivotally connected atone end to an outward end of said press drive arm and moved in generallyreciprocal movement thereby, an L-shaped slot arm fixedly mounted nearone end thereof on a shaft, said shaft pivotally mounted on said firstframe and having each drive arm connected thereto, each slot arm beingadjustably connected near its opposite end to said rod, said camengaging a cam follower mounted on said first frame to pivotally movesaid second frame about said pivot point, said cam including a presslift cam having a varying radius, said cam and said linking means beingmoved by said power drive shaft driven by said press drive means tocause a related movement of said second frame and said drive armssufficient to prevent creep of said carriage assemblies on said armswhile said second frame continues to pivot upward when said press drivearm sweeps through an arc bridging the lowest point on its circle ofrotation while said press lift cam engages said cam follower across thegreatest radius of said cam.
 15. In a printing press having a firstfixed frame, a bed supported on said frame having an upwardly facingsurface to receive work to be printed, a second frame mounted forpivotal movement on said first frame, a pair of spaced-apart armsmounted on said second frame for movement therewith, a chase pivotallymounted beneath said arms and positioned over said work on said bedduring printing, a screen removably mounted on said chase, a carriageassembly mounted on each of said arms for movement therealong, a drivearm connected to each of said carriage assemblies, press drive meansmounted on said second frame and operatively connected to each drive armto drive each drive arm and thereby move each of said carriageassemblies in associated, reciprocal fashion along said arms, theimprovements including pivot points disposed on opposite sides of saidfirst frame and forming a horizontal axis about which said second frameis pivotally moved during a printing cycle, said pivot points disposedgenerally in the horizontal plane of said surface of said bed adjacent arear edge of said surface and allowing a rear portion of said secondframe on which said press drive means is mounted to be swung below saidhorizontal plane of said surface of said bed during the printing cycleto prevent smearing contact between said screen and said work on saidbed by never allowing any portion of said screen to move below thehorizontal plane of said pivot points during movement of said secondframe, and each drive arm being pivotally mounted on said first fixedframe and being driven by said press drive means in an operative,synchronized relationship to the movement of said second frame upwardwith respect to said bed such that said carriage assemblies aremaintained adjacent a selected point along said arms during said upwardmovement of said second frame to eliminate dripping of ink on said work,each of said carriage assemblies including a carriage housing movablymounted on each of said arms, said drive arm being connected to eachcarriage housing to reciprocally move each carriage housing along saidarms during the printing cycle, means pivotally mounted on each carRiagehousing for supporting a squeegee and a flood bar in associatedrelationship for movement relative to each other corresponding to themovement of said screen over said bed, a shuttle contained in eachcarriage housing, stop means mounted on said arms near opposite endsthereof for engaging said shuttle, said stop means causing said shuttleto be automatically reversibly moved within each carriage housing uponengagement therewith, as each carriage housing is moved adjacentthereto, said shuttle operatively connected to said means supportingsaid squeegee and said flood bar to pivot said means supporting saidsqueegee and said flood bar to shift said squeegee and said flood barrelative to each other to automatically and properly position the sameduring movement of said carriage assemblies on said arms.
 16. A printingpress including a first fixed frame, a bed supported on said frame andhaving an upwardly facing surface to receive work to be printed, asecond frame pivotally mounted on said first frame, a pair ofspaced-apart arms mounted on said second frame for pivotal movementtherewith toward and away from said bed, a chase pivotally mountedbeneath said arms and positioned over said work on said bed duringprinting, a screen removably mounted on said chase, a carriage assemblymounted on each of said arms for movement therealong, each of saidcarriage assemblies having a carriage housing supported on said arm,parallelogram means pivotally mounted on each carriage housing forsupporting a squeegee and a flood bar in associated relationship forpivoting movement relative to each other, a free sliding shuttlecontained in each carriage housing and movable with respect thereto,said shuttle operatively connected to said parallelogram means to pivotsaid parallelogram means to shift said squeegee and said flood bargenerally vertically with respect to one another upon movement of saidshuttle relative to said carriage housing, drive arms pivotally mountedon said first frame and connected to each of said carriage housings,press drive means mounted on said second frame and operatively connectedto said drive arms to drive said drive arms and thereby move saidcarriage assemblies reciprocally along said arms, and stops disposednear opposite ends of each of said arms to engage opposite ends of saidshuttle when said carriage assemblies are moved adjacent said stops andmove said shuttle within each carriage housing to shift said squeegeeand said flood bar relative to each other, the operative relationshipbetween the pivotal movement of said second frame and the movement ofsaid drive arms being such that said carriage assemblies are maintainedadjacent said stops following a printing stroke for a desired period fortime while said second frame is being pivoted on said first frame upwardfrom said bed thereby to eliminate creep of said carriage assembliesalong said arms and resulting dripping of ink upon said work.
 17. Theprinting press set forth in claim 16 wherein a first member of saidparallelogram means may be moved with respect to a second member of saidparallelogram and maintained in position by a push arm means to converteach carriage assembly to a non-flood scoop printing operation.